Apple is scheduled to report their fiscal 2011 third quarter earnings next Tuesday so analysts are running their spreadsheets like crazy. We know Apple’s retail business grew a whopping 80 percent year-over-year, accounting for one-fifth of all sales growth by publicly traded retailers in the US and making them the nation’s fastest-growing retailer. Apple’s June quarter performance is especially important in lights of the soft patch which struck the economy. Make no mistake about it, the pundits will be interpreting any slow-down in Apple’s sales as a sign of a larger decline in consumer spending.

Analysts polled byFortune are expecting exceptionally strong Mac sales ranging from 3.8 million units (a twelve percent annual increase) on the low-end, all the way up to 4.63 million units, translating into a cool 33 percent annual growth for the Mac. For comparison, during the March quarter Apple reported sales of 3.67 million Macs, a 28 percent over the year-ago quarter.

Even the most conservative estimates far exceed the not-so-rosy state of the PC industry. Global PC shipments decelerated considerably and grew between 2.3 percent (Gartner) and 2.6 percent (IDC), a material drop from the twelve percent growth IDC report in the first quarter of 2010. To put it bluntly, almost all first-tier PC vendors reported negative growth except Apple. More data points and IDC’s and Gartner’s preliminary numbers right below the fold.

Apple was the only elephant in the room – the company outpaced the industry by a large margin. Strong Mac sales combined with the “ongoing contraction” of the netbook market and consumers turning to tablets enabled Apple to climb from the fifth place and overtake Toshiba and Acer to become the third-largest computer vendor in the US with an estimated market share of 10.7 percent – and that’s excluding the iPad. “The preliminary findings show Apple’s performance far exceed the industry average, partly driven by an iMac refreshment that attracted both consumers and buyers in the education sector”, Gartner wrote.

Hewlett-Packard and Dell continue to lead the pack with 26.9 and 22.6 percent market share, respectively. With an estimated eight million iPads presumably sold during the June quarter thrown into the picture, Apple becomes the nation’s leading computer vendor in terms of shipments and the world’s second-largest PC maker, dwarfed only by Hewlett-Packard which shipped an IDC-estimated 14.88 million units globally (4.55 in the United States).